Abstract
In this paper, using a 3D magnetohydrodynamics (MHD) numerical simulation, we investigate the propagation and interaction of the three halo CMEs originating from the same active region during 4–5 November 1998 from the Sun to Earth. Firstly, we try to reproduce the observed basic features near Earth by a simple spherical plasmoid model. We find that the first component of the compound stream at 1 AU is associated to the first CME of the three halo CMEs. During the propagation in the interplanetary space, the third CME overtakes the second one. The two CMEs merge to a new, larger entity with complex internal structure. The magnetic field of the first CME in the three successive CMEs event is compressed by the following complex ejecta. The interaction between the second and third CME results in the deceleration of the third CME and the enhancement of the density, total magnetic field and south component of the magnetic field. In addition we study the contribution of a single CME to the final simulation results, as well as the effect of the CME–CME interactions on the propagation of an isolated CME and multiple CMEs. This is achieved by analysing a single CME with or without the presence of the preceding CMEs. Our results show that the CME moves faster in a less dense, faster medium generated by the interaction of the preceding CME with the ambient medium. In addition, we show that the CME–CME interactions can greatly alter the kinematics and magnetic structures of the individual events.
Highlights
Coronal Mass Ejections (CMEs) are powerful solar eruptions that release huge amount of mass into the interplanetary medium (IPM)
The fronts of the three CMEs are shown as the isosurfaces of ρ = 1.5ρwind and false color representations of velocity magnitude cover the isosurfaces, where ρwind is the density of the background solar wind
According to the solar wind data observed by Wind, the first shock arrives at 1 AU with density 16 cm−3 and velocity 530 km s−1, and the second component with velocity 635 km s−1 and maximum density 36 cm−3
Summary
Coronal Mass Ejections (CMEs) are powerful solar eruptions that release huge amount of mass into the interplanetary medium (IPM). September 2017 by using the EUHFORIA model [36], investigating the role of CME–CME interactions as a source of the associated intense geomagnetic storm (Dstmin = −142 nT on September 7) These numerical studies enhance our understanding about how CME–CME interactions alter their trajectories, morphologies, kinematics, and magnetic structures. Few of these studies focus on the contribution of a single CME in the CME–CME interaction for real multiple interacting CMEs event by using 3D MHD simulation. The successive CMEs with a similar direction provide a good example of potential interactions of CMEs. Here, we analyze the contribution of single CME to the final simulation results and the effect of the CME–CME interactions on the propagation of a single CME, as well as multiple CMEs. The organization of the paper is as follows.
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